1. Field of the Invention
The present invention relates generally to clamping devices. More particularly, the invention concerns a quick set and release C-clamp.
2. Discussion of the Prior Art
C-clamps are old in the art. The conventional C-clamp comprises a generally C-shaped frame having a first end provided with a threaded bore and a second, opposite end provided with a flat, object engaging surface. An elongated threaded screw is threadably relievable within the threaded bore and includes an object engaging end which cooperates with the flat object engaging surface of the C-shaped frame to clamp an article within the throat of the C-clamp. Adjustment of this common type of C-clamp is accomplished by rotating the threaded screw into and out of the threaded bore. Because screw speed is limited by the pitch of the threads formed within the threaded bore, adjustment of the conventional C-clamp is undesirably slow. For this reason a number of different types of quick set and release C-clamp constructions have been suggested.
Representative of the prior art quick set and release C-Clamps is that disclosed in U.S. Pat. No. 4,502,307 issued to Wang. The Wang device includes a C-shaped body for a screw which can adjustably penetrate through an end of the C-shaped body to clamp and release an object placed within the throat between a free end of a screw and the other end of the C-clamp, "C" shaped body. The device also includes a controlling member mounted pivotally with respect to the C-shaped body and provided with a threaded surface which can be rotated pivotally to engage or disengage with a screw. With this arrangement one can achieve either determine a fast operation mode or a normal operation mode of the C-clamp.
Another prior art quick set and release C-clamp is disclosed in U.S. Pat. No. 5,568,916 issued to Gibbons et al. This device comprises a frame having an inner leg and outer leg fixedly spaced from each other, a threaded rod freely movable through a transverse bore provided in the end portion of the inner leg; a first work piece engaging member fixedly attached to the end of the outer leg; a second work piece engaging member connected to the threaded rod; a pair of rod engagable half bodies slidable within a tapered end of the transverse bore for engaging the threaded rod; a retaining cover to house and restrict movement of the rod engaging half bodies; a detent to urge the half bodies into the seat portion of the transverse bore and to engage the threaded rod; a spring to urge the rod engagable half body slightly out of the tapered end of the transverse bore; a biased element for urging separation of the rod engagable half bodies; and a spring member to urge the detent against the cover.
While the prior art quick set and release clamping devices are clearly superior to the conventional, slow acting C-clamp, they never the less are designed so that the control element must be manually operated by the user in order to permit rapid movement of the threaded rod within the transverse bore. As will be better understood from the description which follows, the apparatus of the present invention overcomes this drawback by providing a novel control means which permits forward or closing movement of the threaded rod without manual operation of the control means or control member of the device. More particularly, the control means of the apparatus of the invention is uniquely designed so that a forward pressure exerted on the threaded rod will cause the control member to pivot downwardly to a position which permits the threads on the threaded rod to by pass the control member so that the threaded rod can be rapidly moved toward a closing position without the necessity for manual operation of the control member or rotation of the threaded rod.